For determining position, all known systems work using satellites, which send a navigation signal, containing information regarding the transmission time, the transmission location and the satellite in question, to the earth. Each satellite sends its own specific navigation signal, which differs from the navigation signals of other satellites. The information regarding the transmission time specifies a precise moment at which the signal was broadcast. The same applies to the transmission location. This information contains the precise data of the path on which the satellite is located at the transmission time. By means of at least four satellites, which broadcast different navigation signals, it is possible for a receiver on the earth to be able to calculate its exact location on the basis of transit time differences.
It is problematic that there are many locations in which the navigation signals broadcast by the satellites are not or are only insufficiently received, meaning that the receiver cannot or can only very imprecisely determine its position. In particular, these include the interiors of buildings, such as shopping centres or car parks, as well as tunnels, ravines, caves and narrow streets surrounded by tall houses.
On the one hand, the need for exact position determination is important so as to be able to reach the desired destination by the shortest route. On the other hand, position determination of this type is also desirable in emergency situations so as to be able to communicate the position of the victim to emergency services.
To overcome these problems, location-based navigation is possible in buildings nowadays by means of a wide range of technical solutions. For example, different wireless systems/networks can be used, which are set out for example by WLAN, Bluetooth and corresponding standards. The position of the receiver may for example be determined by triangulation, by way of power measurement and comparison with the communicating signals. It is equally possible to place individual “radio nodes” at particular locations, which make it possible for the receiver to determine its own location in combination with a card specially provided for this region. However, by comparison with the known global navigation satellite systems, these location determination methods require further radio technologies, mathematical methods and thus additional programs, which first for example have to be installed on the receiving device.
For these reasons, solutions are being created which also make location determination possible outside the direct GNSS coverage region. EP 2 233 943 A1 discloses a method for providing position information by means of an interior transmitter. The interior transmitter receives superposed navigation signals of a plurality of satellites, which have been recorded by a receiver outside a building. In addition to the received navigation signals, the interior transmitter receives a further piece of information specifying its own location. From the received navigation signals and its own location, the interior transmitter calculates a modified position signal as a sum of individual navigation signals as a function of the location of the receiver, and broadcasts said modified position signal.
The drawbacks of EP 2 233 943 A1 are that at least four individual navigation signals have to be conveyed to the interior transmitter and that the interior transmitter itself has to process these navigation signals further so as ultimately to broadcast a navigation signal which passes on the location of the interior transmitter using a receiving device. For this purpose, complex and thus expensive interior transmitters are required.
The object is therefore to provide a method and device by means of which exact location determination is possible, in as simple and cost-effective a manner as possible, at locations at which direct reception of navigation signals from navigation satellite systems is not possible.
For the method for generating and providing individual position information for location determination on the basis of the global navigation satellite system, the object is achieved by the features of claim 1. Further, for the device for generating and providing individual position information for location determination on the basis of the global navigation satellite system, the object is achieved by the features of claim 14. In the associated dependent claims, advantageous developments of the method according to the invention and of the device according to the invention are set out.
The method according to the invention and the device according to the invention for generating and providing individual position information for location determination on the basis of the global navigation satellite system provides employing or using a preparation unit and at least two or at least three or at least four or at least five local position transmitters, the local position transmitters being connected to the preparation unit. Preferably at least four different navigation signals are supplied to the preparation unit, each of which corresponds to a satellite signal on the basis of the global navigation satellite system. Preferably, each of these at least four different navigation signals at least includes information regarding the transmission time and transmission location. The preparation unit is formed to generate at least four target-location-dependent navigation signals by time-shifting at least two, three or preferably all four different navigation signals, the target location coordinates which can be achieved as a result, in other words the position information on the basis of the global navigation satellite system, corresponding to the target location, which may be selected as desired. These at least four target-location-dependent navigation signals are superposed by the preparation unit to form a modified summed navigation signal, and are conveyed to the associated local position transmitter. For each of the local position transmitters, an individual summed navigation signal is generated. It is particularly advantageous for a modified summed navigation signal which is transmitted to the at least one local position transmitter to be generated centrally, in other words by the preparation unit. This makes it possible for the central position transmitter to be able to consist solely of an omnidirectional antenna in the simplest case. Preferably, the summed navigation signal is a digital signal, and so the local position transmitter includes at least one D/A convertor and optionally an amplifier. The digital summed navigation signal can thus be transmitted via known, in particular wired communications channels, such as Ethernet (LAN/Internet), using known protocols. Some or all of the local position transmitters may jointly use some of the transmission paths. This means that some of the individual summed navigation signals are transmitted to the local position transmitters via the same communications channel. As a result, a pre-existing infrastructure can be used, or the costs of constructing a new infrastructure can be kept to a minimum. The local position transmitters may therefore be made very compact and cost-effective.
This construction according to the invention is also in complete contrast to the construction of DE 10 2012 007 205 B5. This document teaches decentralised generation of the target-location-dependent navigation signals. The target-location-dependent navigation signals are generated wherever they are to be broadcast from. This document teaches the use of a position transmitter (pseudolite), which is for supplying a region having limited reception of GNSS navigation signals. The pseudolite shown comprises a signal generation unit having corresponding amplifiers and exactly one antenna. The signal generation unit generates at least three signals, which are modelled on GNSS navigation signals from satellites, and broadcasts these signals using the antenna. No digital superposition of the individual target-location-dependent navigation signals takes place. The pseudolite is installed directly where reception is desired, as an independently operating unit. This means that a pseudolite has to be placed for each target location. Transmission of the target-location-dependent navigation signals via communications networks, either pre-existing or to be newly set up, is not provided. The approach for providing GNSS position information is thus exactly the reverse of that according to the present invention, and is not an economical and scalable solution for multiple target locations.
Further, in the present invention, it is also not necessary for all navigation signals to be time-shifted. Specifically, depending on the satellite arrangement, it may in some cases occur that the position of the target location has only changed with respect to three or even only with respect to two of the at least four satellites.
Further, in the method according to the invention and in the device according to the invention, it is advantageous if the target location is a location which is in radio range of the associated local position transmitter (31, 32, 33, . . . , 3n). The fact that the target coordinates correspond to a target location which is solely in radio range of the at least one local position transmitter makes it possible for the target coordinates for example to represent the centre of a room, the local position transmitter being arranged at the edge of the room. As a result, the maximum deviation of the measured position from the actual position of the receiver is reduced.
Further, it is advantageous if the method according to the invention and the device according to the invention provide selecting at least four satellites, which are in orbit above the location of the connected position transmitter, and if at least four real satellite signals are received from these at least four selected satellites. Alternatively, it is also possible for at least four artificial satellite signals to be generated which are modelled on the real satellite signals of the at least four selected satellites. The at least four received real or at least four received generated satellite signals are navigation signals which are also broadcast by the selected satellites. It is also possible for both real satellite signals and artificially generated satellite signals to be used jointly, in other words mixed together, as long as there are at least four different satellite signals in total. These satellite signals, which are the navigation signals, are supplied to the preparation unit for further processing. It is particularly advantageous that it is possible to select at least four satellites which are located in orbit above the location of the local position transmitter. This means that a direct line of sight between these satellites and the location of the at least one position transmitter would be possible if for example there were no building structures in the way. The satellites are therefore in the field of vision of the local position transmitter. As a result, the local position transmitters can broadcast navigation signals modelled on those which a receiver at the position of the local position transmitter would also have received if the navigation signals of these satellites were received directly. This prevents “confusion” of the receiving device (for example a GPS receiver), which for example had direct satellite reception before entering a building. If a receiving device of this type suddenly received completely different satellites, the functionality thereof would potentially no longer be provided for a period of for example several minutes.
Further, in the method according to the invention and in the device according to the invention, it is advantageous if a selection unit solely selects the satellites which are furthest away from one another and/or which broadcast a satellite signal which is incident on the ground at an angle of more than 5°, preferably more than 10°, more preferably more than 20° at the location of the local position transmitter. This ensures that a receiving device, by means of the modified summed navigation signal broadcast by the local position transmitter, obtains position details, by means of which the altitude of the location can also be exactly determined. It is advantageous that it is made possible for the selection unit not to select satellites of which the satellite signals (or navigation signals) are incident on the ground at an angle of less than 20° or less than 10° or less than 5° at the location of the local position transmitter. Receiving devices such as GPS receivers often would not make use of satellites of this type for position determination because such a shallow angle of incidence in reality generally leads to fading. By way of the selection unit, it is also possible only to select a limited number of satellites which are in orbit vertically or almost vertically above the target location. For example, it can be determined that of the at least four selected satellites there can only be one which is in orbit vertically or almost vertically above the target location. This provides that the preparation unit carries out further processing solely of navigation signals which would also use a receiving device for position determination.
In addition, in the method according to the invention and the device according to the invention, it is advantageous if information regarding a transmission location in the summed navigation signal of the at least four satellites is no more than 5 minutes old, preferably no more than 3 minutes old, more preferably no more than 1 minute old, more preferably no more than 30 seconds old. It is particularly advantageous if the modified summed navigation signal broadcast by each local position transmitter contains location data of the satellites in the form of ephemerides which approximate the actual location of the satellite at the time of broadcast of the modified summed navigation signal as closely as possible. The ephemerides make it possible to draw a conclusion as to the exact position of the satellite, and contain for example the path data of the satellites. Outdated information regarding the location of the satellite can result in some receivers not making use of these satellites for location determination. This problem occurs in particular if a receiving device alternates between directly receiving navigation signals and indirectly receiving navigation signals. “Directly receiving” means that the receiving device obtains navigation signals directly by way of the global navigation satellite system, whilst “indirectly receiving” means that the receiving device obtains navigation signals in the form of modified summed navigation signals which are broadcast for example by the at least one local position transmitter.
Further, in the method according to the invention and the device according to the invention, it is advantageous if a receiving unit is provided, which receives the at least four real satellite signals of the at least four selected satellites, and if this receiving unit is connected to the preparation unit, the at least one receiving unit being a directional antenna and/or an antenna array and/or a mirror and/or a microwave lens, or the receiving unit being a signal generator. In particular, the use of a directional antenna and/or an antenna array and/or a mirror and/or a microwave lens makes interference-free reception of real satellite signals possible, in other words real navigation signals which are preferably not superposed with other signals. The use of a signal generator makes it possible for an artificial satellite signal, in other words an artificial navigation signal modelled on the real satellite signals of the at least four selected satellites, to be able to be generated.
Further, it is advantageous if the method according to the invention and the device according to the invention has at least four antenna arrays and/or at least four directional antennas and/or at least four mirrors and/or at least four microwave lenses, and if a control unit is present which directs and tracks these four antenna arrays and/or the at least four directional antennas and/or the at least four mirrors and/or the at least four microwave lenses onto the selected at least four satellites. Each of the at least four antenna arrays may for example be orientated and tracked onto an associated one of the at least four selected satellites by beamforming. If directional antennas and/or mirrors and/or microwave lenses are used, this is still possible by means of an orientating and tracking unit, which preferably comprises stepper motors. It is particularly advantageous that individual satellite signals, in other words individual navigation signals, are present at the location of the receiving unit, and not a summed navigation signal, which would have to be divided up again. The individual satellite signals, in other words the individual navigation signals, can if required be amplified and supplied to the preparation unit separately. The preparation unit can in this case time-shift the individual navigation signals individually and subsequently superpose them, and thus supply an individually generated summed navigation signal to the local position transmitters.
It is further advantageous according to the invention if the method and the device comprise a GNSS receiver which is connected to the control unit and which conveys location data, in other words an almanac and/or ephemerides, for the at least four selected satellites to the control unit. This makes it possible for the control unit to exactly direct and exactly track each receiver onto the corresponding satellite. It is further advantageous if, for the at least four selected satellites, location data from a memory unit connected to the control unit are conveyed thereto. A memory unit of this type may be a local database or one which is accessible over the Internet and by way of which the current path data, in other words the location data of the satellites, can be queried in real time. It is thus possible for the control unit to direct the receivers exactly onto the associated satellites.
In addition, in the method according to the invention and in the device according to the invention, it is advantageous if at least one of the local position transmitters is part of a transceiver unit which in turn is part of a mobile radio base station and/or if the connection between the preparation unit and at least one of the local position transmitters is a connection which provides the transceiver unit of a mobile radio base station with data. Preferably, the local position transmitters are at least in part connected to the preparation unit via a jointly used (in particular wired) data connection, such as Ethernet. This makes possible simple integration of a local position transmitter into an existing mobile radio network, which for example is constructed inside buildings and provides reception therein, or into a pre-existing network topology. Pre-existing lines and/or antennas may also be used for conveying position data, in other words the modified summed navigation signal.
Finally, in the method according to the invention and the device according to the invention, it is advantageous if the selection unit for generating the modified summed navigation signal selects satellites which are different, entirely or at least in part, for the first local position transmitter and for each further local position transmitter. As a result, regions in which the local position transmitters broadcast the modified summed navigation signal can also overlap in part without fading occurring. This is because the local position transmitters broadcast disjoint summed navigation signals, meaning that a plurality of local position transmitters can coexist without cancellation occurring, in other words superposition of like signals having a different phase. By contrast, if a single local position transmitter is used, cancellations and thus dead spots may occur as a result of reflections. In this case, it would be advantageous for the local position transmitter to have a plurality of antennas, the intention being for the modified summed navigation signal to be broadcast via the various antennas in turn, or for an individual modified summed navigation signal to be conveyed to the local position transmitter for each antenna, it being intended for the satellites selected for each modified summed navigation signal to be different entirely or in part.